Collision avoidance support device

ABSTRACT

A collision avoidance support device comprises target detection unit, target type determination unit, relative position determination unit, target track prediction unit, and vehicle track prediction unit, obstacle determination unit. The vehicle track prediction unit is configured to enlarge said width of a vehicle predicted track compared with a case where an enlargement condition is not satisfied when the enlargement condition is satisfied. The enlargement condition is satisfied when the relative position determination unit detects that a target determined to be a pedestrian by the target type determination unit is positioned on a travel lane at least once.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a collision avoidance support device,which is configured to support a driver so that a vehicle avoidscollision with an obstacle.

2. Description of the Related Art

Hitherto, there has been known a vehicle including a collision avoidancesupport device (for example, Japanese Patent Application Laid-open No.2016-192166).

When a vehicle, on which this collision avoidance support device ismounted, travels on a travel lane of a road, the collision avoidancesupport device detects a target in front of the vehicle with using acamera or/and a radar sensor.

Further, the collision avoidance support device determines the type ofthe detected target with using the detection result. In other words, thecollision avoidance support device determines which of a vehicle, abicycle, a pedestrian, and etc. the detected target is.

Further, the collision avoidance support device calculates a vehiclepredicted track which is a change of position of the vehicle having thecollision avoidance support device during a period of time from thecurrent time until a predetermined period of time passes.

This vehicle predicted track has a predetermined variable width whichvaries depending on the type of the detected target. Specially, when,for example, the target is a vehicle, this variable width becomes asmall value. When the target is a pedestrian, this variable widthbecomes a large value.

Further, when determining that the target is a moving object, thecollision avoidance support device calculates a target predicted trackwhich is a change of position of the target during a period of time fromthe current time until a predetermined period of time passes.

When determining that the target is a moving object, the collisionavoidance support device determines whether or not the vehicle predictedtrack and the target predicted track will interfere with each other.

When determining that the vehicle predicted track and the targetpredicted track will interfere with each other, the collision avoidancesupport device determines that this target is an obstacle being likelyto collide with the vehicle.

When determining that the target is a stationary object, the collisionavoidance support device determines whether or not the target and thevehicle predicted track will interfere with each other.

When determining that the target and the vehicle predicted track willinterfere with each other, the collision avoidance support devicedetermines that this target is an obstacle being likely to collide withthe vehicle.

The collision avoidance support device determines whether or not thisvehicle is highly likely to collide with the obstacle when the vehicle,on which this collision avoidance support device is mounted, continuesto travel while keeping the current traveling state.

When determining that this vehicle is highly likely to collide with theobstacle, the collision avoidance support device executes automaticbrake control.

The collision avoidance support device further determines whether or notthis vehicle is highly likely to collide with the obstacle afterexecuting the automatic brake control.

When determining that this vehicle is highly likely to collide with theobstacle, the collision avoidance support device executes automaticsteering control so that the vehicle avoids collision with the obstacle.

As described above, when the target positioned in front of the vehicle,on which this collision avoidance support device is mounted, is avehicle, the variable width of the vehicle predicted track becomes asmall value. When the target is a pedestrian, this variable widthbecomes a large value. Thus, when the target is a pedestrian, thecollision avoidance support device is easier to execute the automaticbrake control and the automatic steering control compared with the casewhere the target is a vehicle.

However, when the automatic brake control and the automatic steeringcontrol are executed, an occupant of the vehicle is highly likely tofeel uncomfortable. Therefore, the collision avoidance support deviceshould execute the automatic brake control and the automatic steeringcontrol at a minimum necessary frequency.

When the pedestrian is positioned outside of the travel lane, a riskthat the vehicle collides with the pedestrian is smaller compared withthe case where the pedestrian is positioned on the travel lane.

However, the above collision avoidance support device enlarges thevariable width of the vehicle predicted track even when the pedestrianis positioned outside of the travel lane.

Therefore, the collision avoidance support device is easy to executeunnecessary automatic brake control and unnecessary automatic steeringcontrol when the pedestrian is positioned outside of the travel lane.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve theabove-mentioned problem. Specifically, it is an object of the presentinvention to provide a collision avoidance support device capable ofsecurely executing collision avoidance support control having highnecessity and reducing a risk that collision avoidance support controlhaving low necessity is executed by changing an operation condition ofthe collision avoidance support control depending on a position relationbetween a travel lane, on which a vehicle is traveling, and apedestrian.

In order to achieve the above-mentioned object, according to oneembodiment of the present invention, a collision avoidance supportdevice comprises:

target detection means (28) for detecting a target (75, 80) existing infront of a vehicle (10) which travels on a travel lane (71, 71A) of aroad (70, 70A);

target type determination means (28, 33) for determining a type of thetarget detected by the target detection means;

relative position determination means (31) for detecting relativeposition between the travel lane and the target;

target track prediction means (33) for calculating a target predictedtrack (Opov, Opopd) which is a change of position of the target during aperiod of time from current time until a predetermined period of timepasses when the target type determination means determines that thetarget is a moving object;

vehicle track prediction means (32) for calculating a vehicle predictedtrack (Vpo1, Vpo2-b, Vpo2-I) which is a change of position of thevehicle during a period of time from current time until a predeterminedperiod of time passes and has a predetermined width orthogonal in a planview to a travelling direction of the vehicle;

obstacle determination means (34) determining that the target is anobstacle being likely to collide with the vehicle when the targetpredicted track and the vehicle predicted track will interfere with eachother in a case where the target type determination means determinesthat the target is the moving object or when the target and the vehiclepredicted track will interfere with each other in a case where thetarget type determination means determines that the target is astationary object; and

collision avoidance support control means (40, 60) for executingcollision avoidance support control including at least one of alertcontrol which activates alert means (20, 21) of the vehicle andautomatic brake control which activates a brake device (22) of thevehicle.

The vehicle track prediction means is configured to enlarge the width ofthe vehicle predicted track when an enlargement condition is satisfiedcompared with a case where the enlargement condition is not satisfied.The enlargement condition is satisfied when the relative positiondetermination means detects that the target determined to be apedestrian (80) by the target type determination means is positioned onthe travel lane at least once.

In the present invention, the predetermined enlargement condition issatisfied when the relative position determination means detects thatthe target determined to be a pedestrian by the target typedetermination means is positioned on the travel lane at least once.

When the enlargement condition is satisfied, the vehicle trackprediction means enlarges the width of the vehicle predicted trackcompared with a case where the enlargement condition is not satisfied.

Thus, when the pedestrian is positioned on the travel lane, thecollision avoidance support device is easier to execute the collisionavoidance support control compared with the case where the pedestrian ispositioned outside of the travel lane. In other words, when thepedestrian is positioned outside of the travel lane, the collisionavoidance support device is harder to execute the collision avoidancesupport control compared with the case where the pedestrian ispositioned on the travel lane.

When the pedestrian is positioned on the travel lane, a risk that thevehicle collides with the pedestrian is larger compared with the casewhere the pedestrian is positioned outside of the travel lane.

However, in this case, since the vehicle track prediction means enlarges(increases) the width of the vehicle predicted track, the collisionavoidance support control having high necessity is securely executed.

On the other hand, when the pedestrian is positioned outside of thetravel lane, a risk that the vehicle collides with the pedestrian issmaller compared with the case where the pedestrian is positioned on thetravel lane.

However, in this case, since the vehicle track prediction meansdownscales (decreases) the width of the vehicle predicted track, a riskthat the collision avoidance support control having low necessity isexecuted becomes small.

A feature of one embodiment of the present invention resides in that thetarget type determination means is configured to determine whether ornot the target is the pedestrian set number of times, which ispredetermined multiple times, within a predetermined period of time fordetermining condition satisfaction.

The relative position determination means is configured to detect therelative position between the travel lane and the target the set numberof times within the period of time for determining conditionsatisfaction.

The enlargement condition is satisfied when the number of times that therelative position determination means detects that the target, which isdetermined to be the pedestrian by the target type determination means,is positioned on the travel lane is equal to or greater than apredetermined threshold number (Thn), the threshold number being equalto less than the set number of times.

The determination accuracy of the target type determination means may below, and/or the determination accuracy of the relative positiondetermination means may be low.

According to this one of aspects of the present invention, also in thiscase, a risk that the enlargement condition is erroneously satisfied canbe reduced.

In the description given above, in order to facilitate understanding ofthe present invention, names and/or reference symbols in parenthesesused in an embodiment of the present invention described later are addedto components of the invention corresponding to the embodiment. However,respective components of the present invention are not limited to theembodiment prescribed by the reference symbols. Other objects, otherfeatures, and accompanying advantages of the present invention can bereadily understood from a description of the embodiment of the presentinvention provided referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a vehicle to which a collision avoidancesupport device according to an embodiment of the present invention ismounted.

FIG. 2 is a system configuration diagram of the collision avoidancesupport device.

FIG. 3 is a plan view for illustrating an outline of a method todetermine whether or not a vehicle positioned in front of the vehicle,which has the collision avoidance support device and is travelling on astraight travel lane, is an obstacle. This method is executed before thecollision avoidance support device determines whether or not alertcontrol should be executed.

FIG. 4 is a plan view for illustrating an outline of a method todetermine whether or not a pedestrian positioned in front of thevehicle, which has the collision avoidance support device and istravelling on the straight travel lane, is an obstacle. This method isexecuted before the collision avoidance support device determineswhether or not the alert control should be executed.

FIG. 5 is a plan view for illustrating an outline of a method todetermine whether or not the vehicle positioned in front of the vehicle,which has the collision avoidance support device and is travelling onthe straight travel lane, is an obstacle. This method is executed beforethe collision avoidance support device determines whether or notautomatic brake control should be executed.

FIG. 6 is a plan view for illustrating an outline of a method todetermine whether or not the pedestrian positioned in front of thevehicle, which has the collision avoidance support device and istravelling on the straight travel lane, is an obstacle. This method isexecuted before the collision avoidance support device determineswhether or not the automatic brake control should be executed.

FIG. 7 is a plan view for illustrating an outline of a method todetermine whether or not the pedestrian positioned in front of thevehicle, which has the collision avoidance support device and istravelling on a curved travel lane, is an obstacle. This method isexecuted before the collision avoidance support device determineswhether or not the automatic brake control should be executed.

FIG. 8 is a plan view for illustrating avoidance paths of the vehicle.

FIG. 9 is a flowchart for illustrating processing to be executed by asupport ECU.

FIG. 10 is a flowchart for illustrating processing to be executed by thesupport ECU.

FIG. 11 is a flowchart for illustrating processing to be executed by thesupport ECU.

FIG. 12 is a flowchart for illustrating processing to be executed by thesupport ECU.

FIG. 13 is a flowchart for illustrating processing to be executed by thesupport ECU.

FIG. 14 is a flowchart for illustrating processing to be executed by thesupport ECU.

FIG. 15 is a flowchart for illustrating processing to be executed by thesupport ECU.

DESCRIPTION OF THE EMBODIMENTS

Now, referring to the accompanying drawings, description is given of avehicle (automobile) 10 to which a collision avoidance support deviceaccording to an embodiment of the present invention is mounted.

As illustrated in FIG. 1, a windshield 12 formed of a transmissivematerial (e.g., glass or resin) is fixed to a vehicle body 11 of thevehicle 10.

A dashboard 14 is fixed to a front part of the inside of the vehicle 10.A steering wheel 15 is rotatably supported in a right-side part of thedashboard 14.

The vehicle 10 further includes a pair of left and right front wheels16FW and a pair of left and right rear wheels 16RW. The left and rightfront wheels 16FW are steered wheels.

A collision avoidance support mode selection switch (not shown) isarranged on the dashboard 14.

When the collision avoidance support mode selection switch is positionedat an on position, a support ECU 30, a brake ECU 40, a steering ECU 50,and an alert ECU 60 execute collision avoidance support control (alertcontrol, automatic brake control, and automatic steering control)described later. Meanwhile, when the collision avoidance support modeselection switch is positioned at an off position, the support ECU 30,the brake ECU 40, the steering ECU 50, and the alert ECU 60 do notexecute the collision avoidance support control.

The steering wheel 15 and the left and right front wheels 16FW areconnected to each other via a known electric power steering mechanism.Only a part of components of the electric power steering mechanism isillustrated in FIG. 1 and FIG. 2.

The electric power steering mechanism includes a rack shaft extending ina left-and-right direction of the vehicle and slidable in theleft-and-right direction. A pair of left and right tie rods is connectedto left and right ends of the rack shaft, and the left and right tierods are connected to left and right carriers. The left and rightcarriers are rotatable about king pin axes with respect to the vehiclebody 11. Further, the left and right carriers rotatably support the leftand right front wheels 16FW about a horizontal axis, respectively. Apinion shaft meshes with a thread groove formed in the rack shaft. Oneend (lower end) of a steering shaft is connected to the pinion shaft viaa universal joint. Further, the steering wheel 15 is fixed to the otherend (upper end) of the steering shaft.

Accordingly, when the steering wheel 15 is rotated, this rotation forceis transmitted to the steering shaft, the universal joint, and thepinion shaft. Then, the rack shaft meshing with the pinion shaft slidesin one direction out of the left and right directions, and thus steeringangles of the left and right front wheels 16FW linked to the rack shaftvia the tie rods and the carriers change.

The electric power steering mechanism further includes an electric motor18. The electric motor 18 is linked to the rack shaft via a speedreduction mechanism.

The electric power steering mechanism further includes a steering torquesensor 19 for detecting a steering torque (torsion angle) of a torsionbar, which forms a middle portion of the steering shaft.

For example, when the steering torque is generated in the steering shaftas a result of a driver's operation of the steering wheel 15 forrotation, the steering ECU 50 described later calculates a targetsteering assist torque based on the steering torque detected by thesteering torque sensor 19. Further, the steering ECU 50 controls theelectric motor 18 for rotation to cause the electric motor 18 to outputa rotation force corresponding to the target steering assist torque.Then, a torque generated by the electric motor 18 is transmitted to therack shaft, and thus the steering assist is executed.

Further, as illustrated in FIG. 1 and FIG. 2, the vehicle 10 includes abuzzer 20, a display 21, and four friction brake mechanisms 22.

The buzzer 20 is capable of beeping.

The display 21 is a liquid crystal display fixed to the dashboard 14.

Each of the friction brake mechanisms 22 is connected to a brakeactuator 23. The brake actuator 23 is arranged in a hydraulic circuit,which is arranged between a master cylinder (not shown) configured topressurize a hydraulic fluid when a brake pedal is stepped on and eachof the friction brake mechanisms 22. When the brake pedal is stepped on,the hydraulic fluid pressurized by the master cylinder is supplied fromthe brake actuator 23 to the friction brake mechanisms 22, to therebyapply braking forces to the front wheels 16FW and the rear wheels 16RWby the respective friction brake mechanisms 22.

The vehicle 10 further includes wheel speed sensors 25, a yaw ratesensor 26, and an acceleration sensor 27.

The wheel speed sensors 25 are arranged so as to correspond to therespective front wheels 16FW and rear wheels 16RW. Each of the wheelspeed sensors 25 is configured to detect a wheel speed of acorresponding one of the front wheels 16FW and the rear wheels 16RW.

The yaw rate sensor 26 is configured to detect a yaw rate of the vehicle10.

The acceleration sensor 27 is configured to detect a longitudinalacceleration acting in a front-and-rear direction of the vehicle 10 anda lateral acceleration acting in the left-and-right direction (vehiclewidth direction) of the vehicle 10.

The vehicle 10 further includes a surroundings sensor 28. Thesurroundings sensor 28 includes a radar sensor 29 a and a camera 29 b.

The radar sensor 29 a fixed to a front end of the vehicle body 11 isconfigured to radiate a millimeter radio wave around (including at leasta front side of) the vehicle 10. When the radio wave radiated by theradar sensor 29 a is reflected by, for example, a reflector (e.g., apedestrian) positioned around the vehicle 10, the radar sensor 29 areceives the reflected wave. Then, calculation means built in the radarsensor 29 a calculates, based on radiation and reception timings of theradio wave, presence or absence of the reflector and a relativerelationship between the vehicle 10 and the reflector (e.g., thedistance between the vehicle 10 and the reflector and a relative speedbetween the vehicle 10 and the reflector).

The camera 29 b is arranged inside the vehicle 10 so as to be positionedimmediately behind the windshield 12, and is formed using a stereocamera.

The camera 29 b is configured to image a subject (e.g., a pedestrian)positioned in front of the windshield 12.

Calculation means built in the camera 29 b identifies a type of thesubject contained in imaged data acquired by the camera 29 b throughpattern matching that uses the imaged data.

A subject may be a moving object or a stationary object. Examples of themoving object include a pedestrian, a bicycle, and a vehicle(automobile). Examples of the stationary object include a sign board, autility pole, a tree, and a guard rail.

As described later, based on a change in position of the subjectdetected from the imaged data, it can be determined which of the movingobject and the stationary object the subject is.

The camera 29 b is also capable of imaging (recognizing) left and rightwhite lines (lane markers) of a road. The calculation means built in thecamera 29 b calculates the shape of the road and a positionalrelationship between the road and the vehicle 10. The calculation meansof the camera 29 b calculates a positional relationship between the roadand the subject. In other words, the calculation means of the camera 29b recognizes whether or not the subject is positioned between left andright white lines of a travel lane of the road.

Information acquired in this manner by the surroundings sensor 28 isherein referred to as “target information”.

As illustrated in FIG. 2, the collision avoidance support deviceaccording to this embodiment includes the support ECU 30, the brake ECU40, the steering ECU 50, and the alert ECU 60.

The respective ECUs 30, 40, 50, and 60 include microcomputers as maincomponents, and are mutually connected to one another via a controlledarea network (CAN) (not shown) for reception and transmission of varioustypes of control information and request signals. “ECU” is anabbreviation of electric control unit. The microcomputer herein includesa CPU and storage devices (e.g., a ROM and a RAM), and the CPU isconfigured to implement various functions by executing instructions(programs) stored in the ROM.

The support ECU 30 is connected to the wheel speed sensors 25, the yawrate sensor 26, the acceleration sensor 27, and the surroundings sensor28.

The wheel speed sensors 25, the yaw rate sensor 26, the accelerationsensor 27, and the surroundings sensor 28 are configured to repeatedlytransmit their detection results to the support ECU 30 at predeterminedcycles (intervals).

As described later, the support ECU 30 determines, based on the imageddata transmitted from the surroundings sensor 28, whether or not thevehicle 10 is highly likely to collide with the subject (obstacle),which is a target within the imaged data. Then, when it is determinedthat “the vehicle 10 is highly likely to collide with the subject”, thesupport ECU 30 controls the brake ECU 40, the steering ECU 50, and thealert ECU 60. A specific method of controlling the brake ECU 40, thesteering ECU 50, and the alert ECU 60 by the support ECU 30 is describedlater.

The brake ECU 40 is connected to the brake actuator 23.

Thus, even in a case where the brake pedal is not stepped on, when thebrake actuator 23 receives an operation signal from the brake ECU 40,the brake actuator 23 supplies the hydraulic fluid to each of thefriction brake mechanisms 22. Accordingly, also in this case, each ofthe friction brake mechanisms 22 applies braking forces to thecorresponding front wheels 16FW and the corresponding rear wheels 16RW.

The steering ECU 50 is a device configured to control the electric powersteering mechanism, and is connected to the electric motor 18 and thesteering torque sensor 19.

As described above, when the driver operates the steering wheel 15 forrotation, the steering ECU 50 controls the electric motor 18 forrotation to execute a steering assist.

Further, in a case where the driver does not operate the steering wheel15 for rotation, when the steering ECU 50 receives an operation signalfor collision avoidance transmitted from the support ECU 30, thesteering ECU 50 controls the electric motor 18 for rotation inaccordance with the operation signal to steer the front wheels 16FW.

The alert ECU 60 is connected to the buzzer 20 and the display 21.

When the vehicle 10 is highly likely to collide with the subject, thealert ECU 60 operates in accordance with an operation signal transmittedfrom the support ECU 30. Specifically, the alert ECU 60 causes thebuzzer 20 to beep to alert the driver to the possibility of collision,and causes the display 21 to display an operation state of the collisionavoidance support control.

Next, functions of the support ECU 30 are described.

From the functional viewpoint of the support ECU 30, the support ECU 30includes a lane recognition unit 31, a vehicle track calculation unit32, a subject track calculation unit 33, an obstacle determination unit34, a collision determination unit 35, a target deceleration calculationunit 36, an avoidance target track calculation unit 37, and a controlunit 38.

The lane recognition unit 31 is configured to generate information on aroad on which the vehicle 10 travels based on the target informationtransmitted from the surroundings sensor 28. For example, the lanerecognition unit 31 uses a two-dimensional coordinate system having anorigin at a center of the front end of the vehicle 10 and extending inthe left and right directions and the front direction from the origin togenerate coordinate information (positional information) on each ofground, the subject, and the left and right white lines of the road. Inthis manner, the lane recognition unit 31 recognizes the shape of thetravel lane of the vehicle 10 defined by the left and right white lines,the position and direction of the vehicle 10 within the travel lane, andrelative positions of the ground and the subject (reflector, which maybe an obstacle) with respect to the vehicle 10. The lane recognitionunit 31 updates the coordinate information every time the lanerecognition unit 31 receives the target information transmitted from thesurroundings sensor 28.

The vehicle track calculation unit 32 is configured to calculate aturning radius of the vehicle 10 based on the yaw rate detected by theyaw rate sensor 26 and a vehicle speed, which is calculated through useof the wheel speeds detected by the wheel speed sensors 25. The vehicletrack calculation unit 32 is further configured to calculate a track ofthe vehicle 10 based on the calculated turning radius. The track of thevehicle 10 is a change in position of the vehicle 10 during a period oftime from a current time until a predetermined period of time passes,and has a predetermined width orthogonal in plan view to a travelingdirection of the vehicle 10. The track of the vehicle 10 calculated inthis manner is hereinafter referred to as “predicted vehicle track”.

The subject track calculation unit 33 is configured to determine, basedon information on a change in position of the subject acquired from theimaged data, which of the moving object and the stationary object thesubject is. In other words, the subject track calculation unit 33determines the type of the subject.

Specifically, when the camera 29 b identifies the type of the subjectwithin the imaged data through pattern matching, the camera 29 b assignsan individual ID (identification information) to each subject. Then, thesubject track calculation unit 33 uses the ID to identify each subjectwithin the imaged data, and determines whether or not each subject haschanged its position within a predetermined period of time. For example,when a given subject has changed its position within the predeterminedperiod of time, the subject track calculation unit 33 determines that“this subject is a moving object”. Meanwhile, when a given subject hasnot changed its position within the predetermined period of time, thesubject track calculation unit 33 determines that “this subject is astationary object”.

Further, when the subject is the moving object, the subject trackcalculation unit 33 calculates the track of the subject. For example, amoving speed of the subject in the front-and-rear direction (travelingdirection of the vehicle 10) can be calculated based on the vehiclespeed of the vehicle 10 and the relative speed between the vehicle 10and the subject. A moving speed of the subject in the left-and-rightdirection can be calculated based on an amount of change in distancebetween a position of a side end of the subject and the white line,which is detected by the surroundings sensor 28, for example. Thesubject track calculation unit 33 calculates, based on the moving speedsof the subject in the front-and-rear direction and the left-and-rightdirection, a track of the subject, which is a change in position of thesubject (target) during a period of time from the current time until apredetermined period of time passes. The track of the subject calculatedin this manner is hereinafter referred to as “predicted target track”.Alternatively, the subject track calculation unit 33 may calculate thepredicted target track based on the calculated predicted vehicle trackof the vehicle 10 and the distance between the vehicle 10 and thesubject, which is detected by the surroundings sensor 28.

The obstacle determination unit 34 is configured to determine, based onthe predicted vehicle track of the vehicle 10 and the predicted targettrack of the subject being the moving object, whether or not the vehicle10 is likely to collide with the subject when the subject keeps acurrent movement state and the vehicle 10 keeps a current travelingstate (that is, the speed and steering angles of the vehicle 10). Inother words, the obstacle determination unit 34 determines that thevehicle 10 is likely to collide with the subject when the predictedvehicle track and the predicted target track interfere with each other.

The obstacle determination unit 34 is further configured to determine,based on the predicted vehicle track of the vehicle 10 and the positionof the subject being the stationary object, whether or not the vehicle10 is likely to collide with the subject when the subject keeps astationary state and the vehicle 10 keeps the current traveling state.In other words, the obstacle determination unit 34 determines that thevehicle 10 is likely to collide with the subject when the predictedvehicle track of the vehicle 10 and the position of the subjectinterfere with each other.

When determining that the vehicle 10 is likely to collide with thesubject, the obstacle determination unit 34 identifies the subject as anobstacle.

The result of determination made by the obstacle determination unit 34as to whether or not the subject (target) is the obstacle is used forthe alert control and the automatic brake control, which are describedlater. In other words, when the obstacle determination unit 34determines that the subject positioned in front of the vehicle 10 is theobstacle, the alert control and the automatic brake control areexecuted.

The obstacle determination unit 34 determines whether or not the subject(target) is the obstacle using two types of methods.

The result of determination made by one of the methods is used for adetermination on whether or not the alert control should be executed.Hereinafter, this determination method used by the obstacledetermination unit 34 is referred to as “a first determination method”.

The result of determination made by the other of the methods is used fora determination on whether or not the automatic brake control should beexecuted. Hereinafter, this determination method used by the obstacledetermination unit 34 is referred to as “a second determination method”.

FIG. 3 illustrates an outline of the first determination method.

A straight road 70 has only one travel lane 71. That is, the road 70 isa one-way road. The vehicle 10 travels on the road 70 in a direction ofthe arrow. White lines 72 and 73 are drawn on left and right side endsof the travel lane 71. A vehicle 75 positioned in front of the vehicle10 is travelling on the travel lane 71 in the direction of the arrow.

The vehicle track calculation unit 32 is configured to calculate aturning radius of the vehicle 10 based on the yaw rate and the vehiclespeed. The vehicle track calculation unit 32 is further configured tocalculate a first vehicle predicted track Vpo1 based on the calculatedturning radius. A width of this first vehicle predicted track Vpo1 isWd1. As illustrated in FIG. 1, a direction of the width Wd1 isorthogonal in plan view to a traveling direction of the vehicle 10. Thewidth Wd1 is shorter than the entire width of the vehicle 10. Specially,the left end of this first vehicle predicted track Vpo1 is positioned onthe right side with respect to the left end of the vehicle 10, and theright end of the first vehicle predicted track Vpo1 is positioned on theleft side with respect to the right end of the vehicle 10.

Meanwhile, the subject track calculation unit 33 is configured tocalculate a target predicted track Opov of the vehicle 75 being a movingobject. A direction of a width of the target predicted track Opov isorthogonal in plan view to a traveling direction of the vehicle 75. Thewidth of the target predicted track Opov is equal to the entire width ofthe vehicle 75.

When a left-and-right direction position (vehicle width directionposition) of a part of the first vehicle predicted track Vpo1 and thatof a part of the target predicted track Opov are coincident with eachother (interfere with each other), the obstacle determination unit 34determines that the vehicle 75 is an obstacle.

In FIG. 3, since a part of the first vehicle predicted track Vpo1 and apart of the target predicted track Opov interfere with each other, theobstacle determination unit 34 determines that the vehicle 75 is anobstacle.

FIG. 4 also illustrates the outline of the first determination method.

A pedestrian 80 is positioned on the travel lane 71. That is, thepedestrian 80 is positioned between the left white line 72 and the rightwhite line 73. The pedestrian 80 is positioned in front of the vehicle10. This pedestrian 80 is going across the travel lane 71 from the leftside thereof to the right side thereof. That is, this pedestrian 80 is amoving object.

The subject track calculation unit 33 is configured to calculate atarget predicted track Opopd of the pedestrian 80 being a moving object.A direction of a width of the target predicted track Opopd is orthogonalin plan view to a moving direction of the pedestrian 80. The width ofthe target predicted track Opopd is equal to the entire width of thepedestrian 80.

When, for example, the pedestrian 80 moves on the travel lane 71 in adirection parallel to the traveling direction of the vehicle 10, thetarget predicted track Opopd is parallel to the traveling direction ofthe vehicle 10.

When a left-and-right direction position (vehicle width directionposition) of a part of the first vehicle predicted track Vpo1 and thatof a part of the target predicted track Opopd are coincident with eachother (interfere with each other), the obstacle determination unit 34determines that the pedestrian 80 is an obstacle.

In FIG. 4, since a part of the first vehicle predicted track Vpo1 and apart of the target predicted track Opopd interfere with each other, theobstacle determination unit 34 determines that the pedestrian 80 is anobstacle.

Meanwhile, FIG. 5 illustrates an outline of the second determinationmethod.

In this case, the vehicle track calculation unit 32 is configured tocalculate a turning radius of the vehicle 10 based on the yaw rate andthe vehicle speed. The vehicle track calculation unit 32 is furtherconfigured to calculate a second vehicle predicted track Vpo2-b based onthe calculated turning radius. A width of this second vehicle predictedtrack Vpo2-b is Wd2-b. A direction of the width Wd2-b is orthogonal inplan view to the traveling direction of the vehicle 10. As illustratedin FIG. 1, the width Wd2-b is shorter than the entire width of thevehicle 10 and the width Wd1 of the first vehicle predicted track Vpo1.The left end of this second vehicle predicted track Vpo2-b is positionedon the right side with respect to the left end of the vehicle 10, andthe right end of the second vehicle predicted track Vpo2-b is positionedon the left side with respect to the right end of the vehicle 10.

When a left-and-right direction position (vehicle width directionposition) of a part of the second vehicle predicted track Vpo2-b andthat of a part of the target predicted track Opov are coincident witheach other (interfere with each other), the obstacle determination unit34 determines that the vehicle 75 is an obstacle.

In FIG. 5, since the second vehicle predicted track Vpo2-b and thetarget predicted track Opov do not interfere with each other, theobstacle determination unit 34 does not determine that the vehicle 75 isan obstacle.

FIG. 6 also illustrates the outline of the second determination method.

A pedestrian 80 positioned on the road 70 stands still. That is, thispedestrian 80 is a stationary object. The pedestrian 80 is positionedbetween the left white line 72 and the right white line 73.

In this case, the vehicle track calculation unit 32 is configured tocalculate a turning radius of the vehicle 10 based on the yaw rate andthe vehicle speed. The vehicle track calculation unit 32 is furtherconfigured to calculate a second vehicle predicted track Vpo2-I based onthe calculated turning radius. A width of this second vehicle predictedtrack Vpo2-I is Wd2-I. A direction of the width Wd2-I is orthogonal inplan view to the traveling direction of the vehicle 10. As illustratedin FIG. 1, the width Wd2-I is shorter than the entire width of thevehicle 10 and is longer than the width Wd2-b. It should be noted thatthe width Wd2-I may be shorter than the width Wd1, or may be equal to orlonger than the width Wd1. The left end of the second vehicle predictedtrack Vpo2-I is positioned on the right side with respect to the leftend of the vehicle 10, and the right end of the second vehicle predictedtrack Vpo2-I is positioned on the left side with respect to the rightend of the vehicle 10.

When a left-and-right direction position (vehicle width directionposition) of a part of the second vehicle predicted track Vpo2-I andthat of a part of the pedestrian 80 are coincident with each other(interfere with each other), the obstacle determination unit 34determines that the pedestrian 80 is an obstacle.

In FIG. 6, since a part of the second vehicle predicted track Vpo2-I anda part of the pedestrian 80 interfere with each other, the obstacledetermination unit 34 determines that the pedestrian 80 is an obstacle.

As described above, in the second determination method, only when thetarget positioned in front of the vehicle 10 is the pedestrian 80positioned between the left white line 72 and the right white line 73,the vehicle track calculation unit 32 calculates the second vehiclepredicted track Vpo2-I.

In other words, in the second determination method, the vehicle trackcalculation unit 32 calculates the second vehicle predicted track Vpo2-bwhen, for example, the vehicle 75 is positioned in front of the vehicle10, and the pedestrian 80 is positioned on the left side with respect tothe left white line 72 (is positioned outside of the travel lane 71) asillustrated by the virtual line of FIG. 6.

It should be noted that, when the target positioned in front of thevehicle 10 is the pedestrian 80 positioned between the left white line72 and the right white line 73 of the road 70, the obstacledetermination unit 34 determines that a predetermined enlargementcondition is satisfied. In other words, when the enlargement conditionis satisfied, the obstacle determination unit 34 sets the width Wd2-I ofthe second vehicle predicted track Vpo2-I to the value larger than thewidth Wd2-b of the second vehicle predicted track Vpo2-b of when theenlargement condition is not satisfied. That is, the obstacledetermination unit 34 enlarges a collision avoidance support area ofwhen the automatic brake control is executed.

Noted that FIG. 7 illustrates the case where the vehicle 10 travels on aroad 70A having a curved shape.

This road 70A has only one travel lane 71A. That is, the road 70A is aone-way road. The vehicle 10 travels on the road 70A in a direction ofthe arrow. White lines 72A and 73A are drawn on left and right side endsof the travel lane 71A. A pedestrian 80 being a stationary object ispositioned on the travel lane 71A.

In this case, the vehicle track calculation unit 32 is configured tocalculate a turning radius of the vehicle 10 based on the yaw rate andthe vehicle speed. The vehicle track calculation unit 32 is furtherconfigured to calculate the second vehicle predicted track Vpo2-1 basedon the calculated turning radius. The planar shape of this secondvehicle predicted track Vpo2-I is a curved shape extending in adirection parallel to a travelling direction of the vehicle 10. Adirection of the width Wd2-I of this second vehicle predicted trackVpo2-I is orthogonal in plan view to the traveling direction of thevehicle 10.

It should be noted that, planner shapes of the first vehicle predictedtrack Vpo1 and the second vehicle predicted track Vpo2-b, which arecalculated by the vehicle track calculation unit 32 when the vehicle 10travels on the road 70A, are, however not illustrated, curved shapesextending in a direction parallel to a travelling direction of thevehicle 10.

The collision determination unit 35 is configured to calculate, based ona distance L between the obstacle and the vehicle 10 and a relativespeed Vr of the vehicle 10 with respect to the obstacle transmitted fromthe surroundings sensor 28, a predicted time to collision TTC, which isa predicted period of time until the vehicle 10 collides with theobstacle, through Expression (1) given below.

TTC=L/Vr   (1)

When the predicted time to collision TTC is equal to or shorter than acollision determination threshold time set in advance, the collisiondetermination unit 35 determines that the vehicle 10 is highly likely tocollide with the obstacle.

In this embodiment, two types of collision determination threshold timesare used. Specifically, a first collision determination threshold timeTTCth1 or a second collision determination threshold time TTCth2 is usedas the collision determination threshold time. The second collisiondetermination threshold time TTCth2 is shorter than the first collisiondetermination threshold time TTCth1.

When the predicted time to collision TTC becomes equal to or shorterthan the first collision determination threshold time TTCth1 under astate in which the obstacle determination unit 34 determines that “thesubject (target) positioned in front of the vehicle 10 is an obstacle”with using the first determination method, the collision determinationunit 35 determines that “the vehicle 10 is highly likely to collide withthe obstacle”.

Then, the alert ECU 60 receives the operation signal from the supportECU 30, and causes the buzzer 20 and the display 21 to operate for apredetermined period of time. Specifically, for the predetermined periodof time, the buzzer 20 beeps and the display 21 displays an operationstate of the collision avoidance support control.

The target deceleration calculation unit 36 is configured to calculate atarget deceleration at which the vehicle 10 is to be decelerated whenthe obstacle determination unit 34 determines that “the subject (target)positioned in front of the vehicle 10 is an obstacle” with using thesecond determination method.

For example, in a case where the obstacle is a stationary object, whenthe vehicle speed (=relative speed) of the vehicle 10 at the currenttime is represented by V, the deceleration of the vehicle 10 isrepresented by a, and a period of time until the vehicle 10 stops (thatis, a period of time until the vehicle speed becomes zero) isrepresented by t, a travel distance X until the vehicle 10 stops can beexpressed by Expression (2) given below.

X=V·t+(1/2)·a·t ²   (2)

The period of time t until the vehicle 10 stops can be expressed byExpression (3) given below.

t=−V/a   (3)

Accordingly, through substitution of Expression (3) into Expression (2),the deceleration a required for stopping the vehicle 10 when the vehicle10 travels for a travel distance D can be expressed by Expression (4)given below.

a=−V ²/2D   (4)

In order to stop the vehicle 10 at a position separated by a distance βfrom the obstacle toward the vehicle 10, it is only necessary to set thetravel distance D to a distance (L−β) obtained by subtracting thedistance β from the distance L detected by the surroundings sensor 28.When the obstacle is a moving object, it is only necessary to calculatethe deceleration a by using the relative speed Vr in place of thevehicle speed V.

The target deceleration calculation unit 36 sets the deceleration acalculated in this manner as the target deceleration. There is a limitvalue to the deceleration of the vehicle 10 (e.g., approximately −1 G).Thus, when an absolute value of the calculated target deceleration islarger than a limit value (upper limit value) set in advance, the targetdeceleration calculation unit 36 sets the limit value as the absolutevalue of the target deceleration.

When the predicted time to collision TTC becomes equal to or shorterthan the second collision determination threshold time TTCth2 after thealert ECU 60 causes the buzzer 20 and the display 21 to operate, thecollision determination unit 35 determines that “the vehicle 10 ishighly likely to collide with the obstacle”.

Then, the control unit 38 transmits to the brake ECU 40 an operationsignal indicating the target deceleration calculated by the targetdeceleration calculation unit 36. The brake ECU 40 then controls thebrake actuator 23 based on the target deceleration. The friction brakemechanisms 22 then apply friction braking forces to the front wheels16FW and the rear wheels 16RW. In other words, the automatic brakecontrol is executed.

The avoidance target track calculation unit 37 is configured tocalculate an avoidance target track (avoidance path) through which thevehicle 10 may pass to avoid collision with the obstacle when theobstacle determination unit 34 determines that “the subject (target)positioned in front of the vehicle 10 is an obstacle” with using thesecond determination method.

For example, as illustrated in FIG. 8, the avoidance target trackcalculation unit 37 calculates (identifies) a path A through which thevehicle 10 passes when it is assumed that the vehicle 10 travels whilekeeping the current travel state. Specifically, the avoidance targettrack calculation unit 37 calculates the current path A based on alateral acceleration Gy0 currently acting on the vehicle 10 in adirection of an arrow LT. Then, the avoidance target track calculationunit 37 identifies a path B1 through which the vehicle 10 is predictedto pass when a maximum change amount ΔGy of a lateral force that may acton the vehicle 10 is added to the current lateral acceleration Gy0. Themaximum change amount ΔGy is a maximum value of a change amount of thelateral force that does not inhibit the vehicle 10 from safely turningat the vehicle speed at the current time. The avoidance target trackcalculation unit 37 further calculates (identifies) a path B2 throughwhich the vehicle 10 is predicted to pass when the maximum change amountΔGy is subtracted from the lateral acceleration Gy0 of the vehicle 10 atthe current time.

The avoidance target track calculation unit 37 calculates a plurality ofpaths B0, which are each obtained by changing the lateral accelerationby a fixed amount, within a range AR of from the path B1 to the path B2in order from, for example, the path B1 to the path B2. Specifically,the avoidance target track calculation unit 37 reduces a change amountof the lateral acceleration from the lateral acceleration correspondingto the path B1 by a fixed amount each in order, to thereby calculate theplurality of paths B0 in order from the path B1 to the path B2.

Further, the avoidance target track calculation unit 37 identifies,among the path B1, the path B2, and the paths B0, a path whose distanceto the obstacle in a width direction of the road on which the vehicle 10travels is larger than a predetermined limit value VI, as a selectedavoidance path that is an avoidance path through which the vehicle 10 isto travel. For example, first, the avoidance target track calculationunit 37 compares the distance between the path B1 and the obstacle withthe limit value VI. When determining that the distance is larger thanthe limit value VI, the avoidance target track calculation unit 37identifies the path B1 as the selected avoidance path.

The selected avoidance path is set within a range in which the vehicle10 does not depart from the travel lane on which the vehicle 10 istraveling and in which the ground is confirmed to be formed.

After identification of the selected avoidance path, the avoidancetarget track calculation unit 37 calculates a target yaw rate forcausing the vehicle 10 to travel along the selected avoidance path.

The collision determination unit 35 determines whether or not “thetravel distance X calculated based on an actual deceleration a andvehicle speed V at the current time is larger than a value (L0−β)obtained by subtracting β from a distance L0 from the vehicle 10 to theobstacle at the current time”. Then, when the travel distance X islarger than the value (L0−β), the collision determination unit 35determines that “the vehicle 10 is highly likely to collide with theobstacle”.

The control unit 38 then calculates a target steering angle at which thetarget yaw rate calculated by the avoidance target track calculationunit 37 can be obtained based on the target yaw rate and the vehiclespeed of the vehicle 10. The control unit 38 then transmits an operationsignal indicating the target steering angle to the steering ECU 50. Thesteering ECU 50 then drives the electric motor 18 based on the targetsteering angle to steer the front wheels 16FW and the rear wheels 16RW.In other words, the control unit 38 executes the automatic steeringcontrol for causing the vehicle 10 to travel along the selectedavoidance path.

In this embodiment, the automatic brake control by the brake ECU 40 andthe automatic steering control by the steering ECU 50 terminate at thesame time when the collision determination unit 35 determines that “apredetermined control termination condition is satisfied”. In this case,the control unit 38 transmits stop signals to the brake ECU 40 and thesteering ECU 50.

In a case where the vehicle speed of the vehicle 10 is zero, even whenthe driver does not steer the steering wheel 15, the vehicle 10 isunlikely to depart from the travel lane on which the vehicle 10 istraveling to an adjacent travel lane. Accordingly, in this embodiment,the control termination condition is satisfied when the vehicle speed ofthe vehicle 10 becomes zero.

Further, in a case where the traveling direction of the vehicle 10 isparallel to the white lines of the travel lane on which the vehicle 10is traveling, even when the driver does not steer the steering wheel 15,the vehicle 10 is unlikely to depart from the current travel lane to theadjacent travel lane.

Still further, when the distance in a width direction of the travel lanefrom the vehicle 10 to one of the left and right white lines of thetravel lane on which the vehicle 10 is traveling is longer than thedistance in the width direction from the vehicle 10 to the other whiteline, and the vehicle 10 is traveling not in parallel to the other whiteline while approaching the one white line, even when the driver does notsteer the steering wheel 15, the vehicle 10 is unlikely to pass throughthe other white line to depart from the travel lane on which the vehicle10 is traveling to the adjacent travel lane.

Accordingly, in this embodiment, the control termination condition issatisfied when the lane recognition unit 31 determines that “thetraveling direction of the vehicle 10 is parallel to the white lines” orwhen the lane recognition unit 31 determines that “the distance in thewidth direction of the travel lane from the vehicle 10 to one of theleft and right white lines of the travel lane on which the vehicle 10 istraveling is longer than the distance in the width direction from thevehicle 10 to the other white line, and the vehicle 10 is traveling notin parallel to the other white line while approaching the one whiteline”.

As described above, in the present embodiment, the obstacledetermination unit 34 determines that the enlargement condition issatisfied when the target positioned in front of the vehicle 10 is thepedestrian 80 positioned between the left and right white lines 72, 73(72A, 73A) of the road 70 (70A). Then, when the enlargement condition issatisfied, the obstacle determination unit 34 sets the width Wd2-I ofthe second vehicle predicted track Vpo2-I to the value larger than thewidth Wd2-b of the second vehicle predicted track Vpo2-b of when theenlargement condition is not satisfied.

Thus, when the pedestrian 80 is positioned on the travel lane 71, thecollision avoidance support device is easier to execute the automaticbrake control compared with the case where the pedestrian 80 ispositioned outside of the travel lane 71. In other words, when thepedestrian 80 is positioned outside of the travel lane 71, the collisionavoidance support device is harder to execute the automatic brakecontrol compared with the case where the pedestrian 80 is positioned onthe travel lane 71.

When the pedestrian 80 is positioned on the travel lane 71, a risk thatthe vehicle 10 collides with the pedestrian 80 is larger compared withthe case where the pedestrian 80 is positioned outside of the travellane 71.

However, in this case, the obstacle determination unit 34 determineswhether or not the pedestrian 80 is an obstacle with using the secondvehicle predicted track Vpo2-I having the width larger than the secondvehicle predicted track Vpo2-b. Thus, the collision avoidance supportdevice can securely execute the automatic brake control having highnecessity.

It should be noted that, when the collision avoidance support deviceexecutes the automatic brake control, the vehicle speed of the vehicle10 is lowered. Thus, a risk that the vehicle 10 collides with thepedestrian 80 is securely reduced by the automatic steering controlwhich is executed after the automatic brake control is started.

On the other hand, when the pedestrian 80 is positioned outside of thetravel lane 71, a risk that the vehicle 10 collides with the pedestrian80 is smaller compared with the case where the pedestrian 80 ispositioned on the travel lane 71.

However, in this case, the collision avoidance support device determineswhether or not the pedestrian 80 is an obstacle with using the secondvehicle predicted track Vpo2-b having a narrow width. Thus, a risk thatthe collision avoidance support device executes the automatic brakecontrol having low necessity is small. Further, a risk that thecollision avoidance support device executes the automatic steeringcontrol having low necessity is also small.

Next, referring to flowcharts of FIG. 9 to FIG. 15, specific processingperformed by the support ECU 30, the brake ECU 40, the steering ECU 50,and the alert ECU 60 is described.

When a position of an ignition switch (not shown) of the vehicle 10 isswitched from an off position to an on position through an operation ofthe ignition switch (not shown), the support ECU 30 repeatedly executesa routine illustrated in the flowchart of FIG. 9 every time apredetermined period of time passes.

First, in Step 901, the support ECU 30 determines whether or not thecollision avoidance support mode selection switch is positioned at theon position.

When determining “Yes” in Step 901, the support ECU 30 proceeds to Step902 to add “1” to the value of a processing number counter.

When finishing the processing of Step 902, the support ECU 30 proceedsto Step 903, and the lane recognition unit 31 determines whether or notthe target is positioned between the left and right white lines of thetravel lane based on target information. It should be noted that, thesurroundings sensor 28 repeatedly obtains target information at apredetermined time interval equal to or less than a time interval inwhich the support ECU 30 executes the routine of FIG. 9. Thus, thetarget information, to which the lane recognition unit 31 refers in Step903, differs according to processing time of Step 903.

When, for example, a target (the vehicle 75, the pedestrian 80) ispositioned between the left and right white lines 72, 73 (72A, 73A) ofthe travel lane 71 (71A) as illustrated in FIGS. 3 through 7, thesupport ECU 30 determines “Yes” in Step 903.

Meanwhile, when, for example, a target (the pedestrian 80) is positionedon the left side with respect to the white lines 72 as illustrated bythe virtual line of FIG. 6, the support ECU 30 determines “No” in Step903.

When determining “Yes” in Step 903, the support ECU 30 proceeds to Step904, and the obstacle determination unit 34 determines whether or notthe target positioned between the left and right white lines 72, 73(72A, 73A) is a pedestrian by referring to target information. It shouldbe noted that, the target information, to which the obstacledetermination unit 34 refers in Step 904, differs according toprocessing time of Step 904.

When, for example, the pedestrian 80 is positioned between the left andright white lines 72, 73 (72A, 73A) as illustrated in FIGS. 4, 6, and 7,the support ECU 30 determines “Yes” in Step 904.

When determining “Yes” in Step 904, the support ECU 30 proceeds to Step905, and the obstacle determination unit 34 adds “1” to the value of apedestrian counter.

When finishing the processing of Step 905, the support ECU 30 proceedsto Step 906 to determines whether or not the value of a processingnumber counter is equal to or more than “three”.

When determining “Yes” in Step 906, the support ECU 30 proceeds to Step907, and the obstacle determination unit 34 determines whether or notthe value of the pedestrian counter is equal to or more than apredetermined threshold number Thn.

This threshold number Thn is recorded in a memory of the support ECU 30.

The obstacle determination unit 34 compares the value of the pedestriancounter that has been added in Step 905 during execution of the routineof this flowchart at the present time and execution of the routine ofthis flowchart, which was carried out a predetermined timesconsecutively before the execution of the routine at the present time,and the threshold number Thn. It should be noted that, in this way, thesupport ECU 30 executes the routine of this flowchart one time at thepresent time and executes the routine the predetermined timesconsecutively before the present time. The total number of this “onetime” and “the predetermined times”, is referred to as “set number oftimes”. Examples of the set number of times is recorded in the memory ofthe support ECU 30.

When, for example, the support ECU 30 executes the processing of Step905 three times (every time) while executing the routine of thisflowchart the latest three times in the case where the threshold numberThn is set to “two times” and the set number of times is set to “threetimes”, the obstacle determination unit 34 determines “Yes” in Step 907.Similarly, when the support ECU 30 executes the processing of Step 905two times while executing the routine of this flowchart the latest threetimes, the obstacle determination unit 34 determines “Yes” in Step 907.In other words, in these cases, the obstacle determination unit 34determines that the enlargement condition is satisfied.

Whereas, when the support ECU 30 executes the processing of Step 905equal to or less than one time while executing the routine of thisflowchart the latest three times, the obstacle determination unit 34determines “No” in Step 907. In other words, in this case, the obstacledetermination unit 34 determines that the enlargement condition is notsatisfied.

The detection accuracy of the surroundings sensor 28 and thedetermination accuracy of the subject track calculation unit 33 may below, and/or the detection accuracy of the lane recognition unit 31 maybe low.

However, since the support ECU 30 determines whether or not theenlargement condition is satisfied using the plurality of processingresults of the surroundings sensor 28, the subject track calculationunit 33, and the lane recognition unit 31, a risk that the enlargementcondition is erroneously satisfied can be reduced compared with the casewhere the support ECU 30 determines whether or not the enlargementcondition is satisfied using only one processing result.

The threshold number Thnr does not need to be “two (times)”. That is,the threshold number Thnr may be a value other than two.

Similarly, the set number of times does not need to be “three (times)”.That is, the set number of times may be a predetermined plural number(times).

It should be noted that, the period of time, which has passed while thesupport ECU 30 executes the routine of the flowchart in FIG. 9 the setnumber of times, is “period of time for determining conditionsatisfaction”.

When finishing the processing of Step 907, the support ECU 30 proceedsto Step 908. Then, the obstacle determination unit 34 sets a supportarea enlargement flag to “1”.

An initial value of the support area enlargement flag is “0”.

When finishing the processing of Step 908, the support ECU 30temporarily terminates the processing of this routine.

When determining “No” in Step 901, 903, or 904, the support ECU 30proceeds to Step 909 to determine whether or not the value of theprocessing number counter is equal to or more than three.

When determining “Yes” in Step 909, the support ECU 30 proceeds to Step907.

Meanwhile, when determining “No” in Step 906, 907, or 909, the supportECU 30 proceeds to Step 910 to set the support area enlargement flag to“0”.

When finishing the processing of Step 910, the support ECU 30temporarily terminates the processing of this routine.

When the position of the ignition switch is switched from the offposition to the on position, the support ECU 30 repeatedly executes aroutine illustrated in the flowchart of FIG. 10 every time apredetermined period of time passes.

First, in Step 1001, the support ECU 30 determines whether or not thecollision avoidance support mode selection switch is positioned at theon position.

When determining “Yes” in Step 1001, the support ECU 30 proceeds to Step1002, and the obstacle determination unit 34 determines whether or notthere is an obstacle in front of the vehicle 10. Specially, the obstacledetermination unit 34 determines whether or not a target positioned infront of the vehicle 10 is an obstacle using the first vehicle predictedtrack Vpo1.

When determining “Yes” in Step 1002, the support ECU 30 proceeds to Step1003, and the collision determination unit 35 sets an alert flag to “1”.

An initial value of the alert flag is “0”.

When determining “No” in Step 1001 or 1002, the support ECU 30 proceedsto Step 1004, and the collision determination unit 35 sets the alertflag to “0”.

When finishing the processing of Step 1003 or 1004, the support ECU 30temporarily terminates the processing of this routine.

When the position of the ignition switch is switched from the offposition to the on position, the support ECU 30 repeatedly executes aroutine illustrated in the flowchart of FIG. 11 every time apredetermined period of time passes.

The processing of Step 1101 is the same as the processing of Step 1001.

When determining “Yes” in Step 1101, the support ECU 30 proceeds to Step1002, and the obstacle determination unit 34 determines whether or notthe support area enlargement flag is “1”.

When determining “Yes” in Step 1102, the support ECU 30 proceeds to Step1103, and the obstacle determination unit 34 enlarges the collisionavoidance support area of when the automatic brake control is executed.

When finishing the processing of Step 1103, the support ECU 30 proceedsto Step 1104, and the obstacle determination unit 34 determines whetheror not there is an obstacle in front of the vehicle 10. Specially, theobstacle determination unit 34 determines whether or not a targetpositioned in front of the vehicle 10 is an obstacle using the secondvehicle predicted track Vpo2-I.

When determining “No” in Step 1102, the support ECU 30 proceeds to Step1104, and the obstacle determination unit 34 determines whether or notthere is an obstacle in front of the vehicle 10. Specially, the obstacledetermination unit 34 determines whether or not a target positioned infront of the vehicle 10 is an obstacle using the second vehiclepredicted track Vpo2-b.

When determining “Yes” in Step 1104, the support ECU 30 proceeds to Step1105, and the collision determination unit 35 sets an automatic brakeflag to “1”. An initial value of the automatic brake flag is “0”.

When finishing the processing of Step 1105, the support ECU 30 proceedsto Step 1106, and the target deceleration calculation unit 36 sets thetarget deceleration.

When determining “No” in Step 1101 or 1104, the support ECU 30 proceedsto Step 1107, and the collision determination unit 35 sets the automaticbrake flag to “0”.

When finishing the processing of Step 1106 or 1107, the support ECU 30temporarily terminates the processing of this routine.

When the position of the ignition switch is switched from the offposition to the on position, the support ECU 30 repeatedly executes aroutine illustrated in the flowchart of FIG. 12 every time apredetermined period of time passes.

The processing of Step 1201 is the same as the processing of Step 1001.

When determining “Yes” in Step 1201, the support ECU 30 proceeds to Step1202 to determine whether or not the automatic brake flag is “1”.

When determining “Yes” in Step 1202, the support ECU 30 proceeds to Step1203, and the collision determination unit 35 sets an automatic steeringflag to “1”. An initial value of the automatic steering flag is “0”.

When finishing the processing of Step 1203, the support ECU 30 proceedsto Step 1204, and the avoidance target track calculation unit 37calculates (identifies) the selected avoidance path.

When determining “No” in Step 1201 or 1202, the support ECU 30 proceedsto Step 1205, and the collision determination unit 35 sets the automaticsteering flag to “0”.

When finishing the processing of Step 1204 or 1205, the support ECU 30temporarily terminates the processing of this routine.

When the position of the ignition switch is switched from the offposition to the on position, the support ECU 30 repeatedly executes aroutine illustrated in the flowchart of FIG. 13 every time apredetermined period of time passes.

In Step 1301, the support ECU 30 determines whether or not the alertflag is “1”.

When determining “Yes” in Step 1301, the support ECU 30 proceeds to Step1302, and the collision determination unit 35 determines whether or notthe predicted time to collision TTC is equal to or shorter than thefirst collision determination threshold time TTCth1.

When determining “Yes” in Step 1302, the support ECU 30 proceeds to Step1303 to transmit the operation signal to the alert ECU 60. Then, thealert ECU 60 causes the buzzer 20 and the display 21 to operate.

When finishing the processing of Step 1303, the support ECU 30 proceedsto Step 1304 to determine whether or not a predetermined period of timehas passed since the buzzer 20 and the display 21 started operating.

When determining “No” in Step 1304, the support ECU 30 repeats theprocessing of Step 1304.

Meanwhile, when determining “Yes” in Step 1304, the support ECU 30proceeds to Step 1305 to transmit a stop signal to the alert ECU 60.Then, the alert ECU 60 stops the buzzer 20 and the display 21.

When finishing the processing of Step 1305, the support ECU 30 proceedsto Step 1306, and the collision determination unit 35 sets the alertflag to “0”.

When the support ECU 30 determines “No” in Step 1301 or 1302, orfinishes the processing of Step 1306, the support ECU 30 temporarilyterminates the processing of this routine.

When the position of the ignition switch is switched from the offposition to the on position, the support ECU 30 repeatedly executes aroutine illustrated in the flowchart of FIG. 14 every time apredetermined period of time passes.

In Step 1401, the support ECU 30 determines whether or not the automaticbrake flag is “1”.

When determining “Yes” in Step 1401, the support ECU 30 proceeds to Step1402, and the collision determination unit 35 determines whether or notthe predicted time to collision TTC is equal to or shorter than thesecond collision determination threshold time TTCth2.

When determining “Yes” in Step 1402, the support ECU 30 proceeds to Step1403 to transmit the operation signal to the brake ECU 40. Then, thebrake ECU 40 starts the automatic brake control while using the targetdeceleration calculated in Step 1106.

When finishing the processing of Step 1403, the support ECU 30 proceedsto Step 1404, and the collision determination unit 35 determines whetheror not the control termination condition is satisfied.

When determining “No” in Step 1404, the support ECU 30 repeats theprocessing of Step 1404.

Meanwhile, when determining “Yes” in Step 1404, the support ECU 30proceeds to Step 1405, and the control unit 38 transmits a stop signalto the brake ECU 40.

When finishing the processing of Step 1405, the support ECU 30 proceedsto Step 1406, and the collision determination unit 35 sets the automaticbrake flag to “0”.

When the support ECU 30 determines “No” in Step 1401 or 1402, orfinishes the processing of Step 1406, the support ECU 30 temporarilyterminates the processing of this routine.

When the position of the ignition switch is switched from the offposition to the on position, the support ECU 30 repeatedly executes aroutine illustrated in the flowchart of FIG. 15 every time apredetermined period of time passes.

In Step 1501, the support ECU 30 determines whether or not the automaticsteering flag is “1”.

When determining “Yes” in Step 1501, the support ECU 30 proceeds to Step1502 to determine whether or not the travel distance X is larger thanthe value (L0−β).

When determining “Yes” in Step 1502, the support ECU 30 proceeds to Step1503 to transmit the operation signal to the steering ECU 50. Then, thesteering ECU 50 causes the electric motor 18 to operate so that thevehicle 10 travels along the selected avoidance path calculated in Step1204. In other words, the steering ECU 50 starts the automatic steeringcontrol.

Detail of control in Step 1504 is the same as that in Step 1404.

When determining “Yes” in Step 1504, the support ECU 30 proceeds to Step1505, and the control unit 38 transmits a stop signal to the steeringECU 50.

When finishing the processing of Step 1505, the support ECU 30 proceedsto Step 1506, and the collision determination unit 35 sets the automaticsteering flag to “0”.

When the support ECU 30 determines “No” in Step 1501 or 1502, orfinishes the processing of Step 1506, the support ECU 30 temporarilyterminates the processing of this routine.

In the above, the collision avoidance support device according to thisembodiment has been described, but the present invention is not limitedto the above-mentioned embodiment, and various changes are possiblewithin the range not departing from the object of the present invention.

For example, the brake ECU 40 may be configured to execute “left andright brake balance adjustment control” corresponding to the automaticsteering control.

The “left and right brake balance adjustment control” is known controlin which magnitudes of the braking forces applied from the frictionbrake mechanisms 22 to the left front and rear wheels 16FW and 16RW andmagnitudes of the braking forces applied from the friction brakemechanisms 22 to the right front and rear wheels 16FW and 16RW are madedifferent from each other, to thereby adjust the traveling direction ofthe vehicle 10.

The automatic steering control and the left and right brake balanceadjustment control are both an example of traveling direction automaticcontrol.

When the driver operates the steering wheel 15 for rotation under astate in which the traveling direction automatic control is beingexecuted, the steering ECU 50 (or the brake ECU 40) may immediatelyterminate the traveling direction automatic control and execute steeringcontrol (or the left and right brake balance adjustment control)corresponding to the driver's steering operation.

The termination time of the automatic brake control and the terminationtime of the traveling direction automatic control may be made differentfrom each other.

The surroundings sensor 28 does not need to include the radar sensor 29a and the camera 29 b. For example, the radar sensor 29 a and amonocular camera may be used to form the surroundings sensor 28.

Information of a navigation system may be used as informationrepresenting the shape of the road (travel lane) on which the vehicle 10travels and the positional relationship between the road and the vehicle10.

Alert means may include only one of the buzzer 20 and the display 21.

What is claimed is:
 1. A collision avoidance support device, comprising:target detection means for detecting a target existing in front of avehicle which travels on a travel lane of a road; target typedetermination means for determining a type of said target detected bysaid target detection means; relative position determination means fordetecting relative position between said travel lane and said target;target track prediction means for calculating a target predicted trackwhich is a change of position of said target during a period of timefrom current time until a predetermined period of time passes when saidtarget type determination means determines that said target is a movingobject; vehicle track prediction means for calculating a vehiclepredicted track which is a change of position of said vehicle during aperiod of time from current time until a predetermined period of timepasses and has a predetermined width orthogonal in a plan view to atravelling direction of said vehicle; obstacle determination meansdetermining that said target is an obstacle being likely to collide withsaid vehicle when said target predicted track and said vehicle predictedtrack will interfere with each other in a case where said target typedetermination means determines that said target is said moving object orwhen said target and said vehicle predicted track will interfere witheach other in a case where said target type determination meansdetermines that said target is a stationary object; and collisionavoidance support control means for executing collision avoidancesupport control including at least one of alert control which activatesalert means of said vehicle and automatic brake control which activatesa brake device of said vehicle, wherein, said vehicle track predictionmeans is configured to enlarge said width of said vehicle predictedtrack when an enlargement condition is satisfied compared with a casewhere said enlargement condition is not satisfied, said enlargementcondition being satisfied when said relative position determinationmeans detects that said target determined to be a pedestrian by saidtarget type determination means is positioned on said travel lane atleast once.
 2. A collision avoidance support device according to claim1, wherein said target type determination means is configured todetermine whether or not said target is said pedestrian set number oftimes, which is predetermined multiple times, within a predeterminedperiod of time for determining condition satisfaction, said relativeposition determination means is configured to detect said relativeposition between said travel lane and said target said set number oftimes within said period of time for determining condition satisfaction,said enlargement condition is satisfied when the number of times thatsaid relative position determination means detects that said target,which is determined to be said pedestrian by said target typedetermination means, is positioned on said travel lane is equal to orgreater than a predetermined threshold number, said threshold numberbeing equal to less than said set number of times.